When entering electronic text in English, the user can enter one character with one key press. In Chinese text, however, a number of key presses are required to identify one character. This is why methods for entering electronic text in Chinese are somewhat distinct from methods for entering English text. Most input editors provide a predictive, associative input method. The user enters the input symbol or symbols describing the character to be entered. The input editor provides a candidate list comprising the characters associated with the input symbol or symbols. The user can then select the desired character from the candidate list. The input editor may also provide a feature, in which, once the first character is selected, the next probable character (or in some cases the whole word or phrase) is displayed. Word association can be quite useful as Chinese words often consist of two characters, and it helps to predict a second character once the first character is entered.
Chinese input methods can be approximately categorized into four types: phonetic, shape, semantic, and code input method. ZhuYin input method is a phonetic input method based on the Chinese phonetic system called BoPoMoFo. The ZhuYin input method is designed especially for entering characters of Mandarin Chinese, and the method is mainly used in Taiwan. According to the ZhuYin method, Chinese characters are built from defined symbols. There are 37 ZhuYin symbols representing vowels and consonants, each describing a certain sound. In addition to symbols, there are five tone marks representing the intonation of the character described by the symbols. The maximum number of symbols describing a Chinese character is three plus a tone mark. When entering electronic text, the symbols and tone marks are entered using a keyboard or corresponding input realization. The input editor incorporates an engine which associates the entered symbols to Chinese characters and provides a candidate list comprising the Chinese characters corresponding to the pronunciation described by the entered symbols. If the engine can recognise the entered string, i.e. the tone mark is added into a valid ZhuYin string, candidates are shown in the candidate list. Otherwise, the candidate list is empty.
ZhuYin symbols and tone marks were originally designed only for creating Chinese characters. Nowadays, however, ZhuYin symbols associated with tone marks exist as part of “e-language” or “chat-language” in Taiwan's Internet community. Their use is similar to the English language's “chat behaviour”: 4 u means “for you”, 2 b means, “to be” and so on. Entering the ZhuYin symbols and tone marks into electronic text requires, however, a special kind of user interface, since the ZhuYin symbols and tone marks were not originally designed to be inserted into text.